Phase reversing means



April 13, 1943. D. M. DAVIS 2,316,567

PHASE REVERSING MEANS F11 1 June 18, 1942 n I?, I3 I0 RADIO AUDIO 18 T AMPLIFIER g RANsmTrER Inventor: David M. Davis,

by fi JAM/ 1 His Attorney Patented Apr. 13, 1943 OFFICE PHASE nevansme MEANS David M. Davis, Rexiorck N. Y., assignor to General Electric Company, a corporation of New York . Application June 18, 1942','Serial No. 447,503

3 Claims.

This invention relates to phase reversing means and-more particularly to means for reversing the phase of electromotiveforce having a wave form which is asymmetrical with respect to its average axis, 1. e., that portion of the electromotive force which is of one polarity is more intense than that of the other polarity.

It has been found that signal electromotive force produced by certain types of signal equip-, ment has peak intensities of one polarity greater than of the other. For example, certain types of microphones convert the human voice, particularly the male voice, into an electrical wave in which the peak intensity of one polarity may be two or more times as great as the peak intensity of the other polarity. of the signal peaks of greater intensity is reversed when the sound impinges on the opposite side of the microphone.

Signal transmission channels generally have an asymmetrical linear transmission characteristic. That is, theyare capable of transmitting faithfully signals of which a particular polarity is more intense than the other. For example, an electron discharge amplifier device may b so arranged that a positive potential may be applied to its input of such value that its control electrode just begins to carry discharge current,

' which positive potential is less than the negative potential which must be applied to the input to cut ofi the flow of discharge current in the device. When so arranged the device is'capable of amplifying a wave whose peaks of one polarity, corresponding to the negative potential, are larger than the peaks of opposite polarity.

Similarly, the carrier wave modulator and amplifier stages of a radio transmitter generally are capable of producing carrier wave power for short periods in amounts considerably greater than four times the power of the carrier wave when unmodulated, but the carrier wave intensity can never be reduced below zero intensity, with the consequence that the intensity of the carrier wave may be modulated vbetween zero intensity and an intensity more than twice 'as great as the intensity of the unmodulated carrier wave.

It is desirable to modulate the intensity of such a carrier wave in accordance with a signal, of which the peaks of one polarity are more intense than the peaks of the other polarity, so that the carrier wave intensity is increased in response to the more intense signal peaks, and decreased in response\to the less intense signal peaks of the opposite polarity. It is an object of my invention to provide an improved and simplified arrangement for transmitting signals of which peaks of one polarity are more intense than peaks of the other polarity through a signal transmission channel in such phase that the channel is ca- Furthermore, the polarity appended claims.

pable of most eiiiciently transmitting such signals.

An arrangement ofthis general nature is disclosed in Patents 2,158,820 and 2,158,821-Hathaway, issued on May 16, 1939, in which the dissymmetry of signals is detected by electronic means. It is an object of my invention to provide in such an arrangement improved and simplified means for detecting such dissymmetry of a signal. It is a further object of my invention to provide in connection with such detecting means improved highly sensitivemeans for reversing the phase of such signals as desired.

. The features of my invention which I believe to be novel are set forth with particularity in the My invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing inwhich Figs. 1

I and 3 illustrate two embodiments of my invention;

' and Fig. 2 indicates certain characteristics of the arrangement of Fig. 1.

In Fig. 1 a microphone l0, which may be excited by sound, produces audio signals which are amplified through an audio amplifier II, and which modulate the intensity of a carrier wave in a radio transmitter 12, which carrier wave is radiated from an antenna l3. As explained previously, it is desired that the signals amplified through amplifier I I be transmitted to the radio transmitter l2 with such polarity that the signal peaks-of greater intensity shall increase the intensity of the carrier wave, while the oppositely 'poled peaks of less intensity shall decrease the intensity of the carrier wave. To this end audio signals from the amplifier l l are impressed on the primary of a transformer H which has a secondary l5, of which a center tap I6 is connected to the radio transmitter I2, while the two terminals I l and I8 are connected respectively to fixed contacts l9 and 20 of a polarized relay 2|.

The relay 2| is arranged, with apparatus to be described hereinafter, so that its armature 22 moves to the left in response to signals from the amplifier ll of which the peaks of one polarity are most intense, and moves to the right in re 'sponse to signals from amplifier l I of which peaks of the other polarity are most intense. The armature 22 carries a movable contact 23, which is connected through a'conductor 24 to the radio transmitter I2. When the armature 22 is in the left-hand position signals from the amplifier II are impressed on the radio transmitter i2 through a circuit extending from the transmitter I2 through center tap Hi, the lower half of secondary ii of transformer l4, terminal I8, fixed contact 20, movable contact'23, and conductor 24. When the armature 22 is in the right-hand posiproduced through tion, signals from the amplifier II are impressed 33 have a time constant such that the voltage in opposite phase on the transmitter 12 through across condenser 33 changes quite slowly. Such a circuit extending from the transmitter [2 changes may be made of the order or the syllabic through center tap it, the upper half of secondary of transformer 14, terminal l1, fixed contact l9, movable contact 23, and conductor 24.

Apparatus is provided to produce a continuous potential whose polarity depends on the polarity of the most intense signal peaks from the amplifier H, and whose intensity depends -.onthe amount 0! dissymmetry of signals from the am plifier ll. This apparatus includes a tertiary winding or the transformer M, one terminal of which is grounded, and the other terminal of which is connected through a. coupling condenser 26 to one terminal of a nonlinear resistance 21, the other terminal of which is grounded. Audio signals from across the non-linear resistance 21 in predetermined phase.

The non-linear resistance 21 is preferably of the type described in United States Patent No. 1,322,742, issued Sept. 8, 1e31, to K. B. McEachron, and assigned to the same assignee as the present application, but may be composed of any material having a. non-linear resistance-current relation.

The action of the non-linear resistance 21 in producing a continuous potential compoent when an asymmetrical signal from the amplifier H is impressed thereacross may be better understood by reference to Fig. 2, in which a. signal wave having pronounced dissymmetry is illustrated. The peaks 3!! of one polarity in Fig. 2 are illustrated as substantially more intense than the peaks 3| of opposite polarity. When the particular material describedin the above-mentioned McEachron patent is utilized as the resistancefl, its resistance decreases as current fiow therethrough increases. That is, a small increase in voltage results in a large increase in current through the resistance. Consequently, the more intense peaks produce a current through the resistance 21 which is proportionately greater than the current the resistance 21 by the less intense peaks 31. tense peaks 30, a greater reactive voltage-drop across condenser 26 exists than would be the case it the resistance 21 had linear characteristics, with the result that the peaks -3l' of the signal wave are more effective in across the resistance 21 than are. the peaks 33.

Although the signal wave shown in Fig. 2 is asymmetrical in nature; having peaks 30 which are or greater intensity'than its oppositely poled peaks -3l the total area under the peaks 30 is ex-. actiy equal to the total area under the peaks 3i of opposite polarity. However, due to the nonlinearresistance current characteristics 0! the resistance 21, the peaks 30 and the peaks 31- are so distorted in the signal as it appears across the resistance 21 that this is no longer the case. In'the voltage wave across peaks corresponding to the peaks3l oi the signal voltage wave across resistance 21 enclose a larger area than the peaks 0! the signal wave across resistance 21. Consequently, there is a unidirectional component of voltage in the resultant wave across the non-linear resistance 21. r

.A resistance 32 and condenser 33 are connected in series between the terminals or the resistance 21. Itis preferred that the condenser 33 be suificiently large to store enough energy to operate the relay 2! after a short time interval and. that the combination of resistance 32. and condenser the resistance 21, the

the amplifier H consequently appear condenser acts to one te the relay. to its rate of the signals from the microphone it.

The operating coil 34 of relay 2| is connected in shunt to the condenser 33 through the normally open contacts oi! a relay 3!. The relay 2i must be sufficiently sensitive to operate in response to the voltage which is developed across condenser 33 by action or the non-iinear resistance 21. As more powerful signals from the amplifier II are impressed'upon the non-linear resistance 21, it is capable of developing a larger voltage across the condenser 33, so that the relay ill need be less sensitive. Whenever the normal- 1y open contacts of relay 35 are closed, and voliage exists across the condenser 33, the relay 2i produces the proper connection between audio amplifier ii through transformer is and radio transmitter It, so that the carrier wave intensity is reduced in response to oi thesignal wave of less intensity, and the carrier wave intensity is increased in response to peaks of the signal wave of greater intensity. This proper connection may be determined by trial, and if it be found that the the polarity of the signal impressed across resistance 21 may be changed, the polarity 01 the voltage impressed on operating coil 34 oi! relay 2! from condenser 33 may be changed; or the polarity o! the connections to the secondary l5 oi. transformer 14 may be changed.

It is desirable that the phase reversing arrangement operate only in the absence of signals from the amplifier ll. Accordingly, a discharge device 40 is provided which is so arranged as to close the normally open contacts oi? relay 3' in the absence of signals, and to maintain those contacts open in. the presence or signals. That is, whenever signals are absent, device 43 energizes relay 33 so that its contacts close and energy stored in the proper position.

producing a voltage 43 is'connected through a t0 groundand is The discharge device 43 may be connected in any suitable manner 'to perform its mmction. and asillustrated is connected as a triode detector. its anode 43 is connected throughthe operating 3! to the positive terminal or a source 44 of potential, the negative terminal 01 the source 44' being grounded. The control electrode 43 or, device grid leak resistance 43 connected through a coupling condenser 41 to the movable contact 43 or a varitable resistance 4,3. of which one terminal is grounded. The ungroundedterminal o! resistto the ungrounded terminal windinglloi transformer l4, so

once 43 is connected or the tertiary that-"audio signals are impressed through condenser 41 upon the control electrode 430! device 43 inintensity determined by contact 43.

The operating time required after the cessation 0d signals from the amplifier ll before relay 35 operates, is determined by the size or! condenser 41 and resistonce 43. The larger this condenser 41 and'resistance 43, the longer the time required for the relay 35 to operate after si'gnalscease. It is .desir-able to znakethis time reasonably long, vent too irequent operation or relay 33. The time, however, must be sufiiciently short to close the contacts od relay 33 before the charge disappears from condenser 33. Condenser 33 has two runctions, one being to separate the continuous connection as first made is wrong coil43ofrela ythe adjustment of so; the detector, that is, the

topre-' potential developed across resistance 21 from the signal potential thereacross, and the other to store such potential until relay 35 operates.

In Fig. 3 there is illustrated an arrangement whereby the relay 2! may be less sensitive. In

this figure many of the elements are similar to those illustrated in Fig. 1, and are given like reference characters. The operating coil 34 in Fig. 3, instead or being connected in shunt to the condenser 33, is connected across one diagonal oi. a bridge circuit, of which the resistance of one arm is influenced by the voltage across condenser 38.

This bridge circuit includes four arms, respectively formed by resistance 50, resistance 5|, ad- Justable resistance 62, and the anode to cathode discharge path of an electron discharge device 58 and resistance 54. A point between resistances 52 and is connected to ground, which is thus at one corner or the bridge, and the opposite corner, between resistances 50 and ii, i connected through the contacts of relay 8! to the positive terminal of source ll. Condenser 33 is connected between the control electrode 55 of device 53 and ground.

The bridge should be adjusted for balance when there are no signals from microphone it. Under such conditions there is no voltage across the condenser and the contacts of relay 3! are held closed by current flowing through device 40. Resistance 54 produces a bias potential between control electrode 55 and cathode 56 of device I53 by reason oi the discharge current of device 53 flowing therethrough. This bias potential developed across resistance as should be of such a value that the potential or control electrode 65 may be changed a substantial amount in either direction without cutting on the discharge current 01' device 63, and without causing the control electrode 55 to become positive with respect to cathod Bi.

With the bias resistance 54 so adjusted, and with no signal from microphone l0. the resistance 52 is adjusted so that substantially no potential exists across the operating coil ll.

, Under such conditions of adjustment, when a potential appears across condenser 33, so as to make the control electrode 85 less negative with respect to ground, device I53 tends totransmit more current and appears as a smaller resistance, thereby unbalancing the bridge. when the bridge is so unbalanced the upper terminal of operating coil 3 i made positive in potential and the relay it operates accordingly.

when the opposite potential appears across condenser 88 and makes the control electrode iii more negative with respect to ground. the device 58 appears as a larger resistance and makes the lower terminal of operating coil 8| positive so as to cause the relay 2| to operate oppositely.

The relay 85 operates as described previously to prevent operation of the relay 2| except in the absence of signals. That is, whenever signals are present, current through the device so is reduced, so that relay ii! is deenergized, thereby diseon necting the source it from the bridge and conse-' quently preventing operation or the relay 2!.

- When si nals disap ear, the device l0, after a time determined by the sire oi the condenser ti and resistance 48, begins to pass current and energizes relay 35, so that its normally own contact; close and supply energy to the bridge, so

ing from my invention in its broader aspects, and 1 I, therefore, aim in the appended claims to cover all such changesand modifications as fall within the true spirit and scope or my invention.

- 'What I claim as new and desire to secure by Letters Patent 01' the United States, is:

1. In combination, in a system for-transmit-- ting an asymmetrical alternating potential through a channel having an asymmetrical linear transmission characteristic, a non-linear resistance, means for impressing said alternating potential across said resistance to develop a continuous potential whose polarity corresponds to the asymmetry of said alternating potential, and

means responsive to the polarity of said continuous potential for supplying said alternating potential to said channel in such phase that the asymmetry of said alternating potential corresponds to the asymmetry of the linear transmission characteristic of said channel.

2. In combination, in a system for transmitting an asymmetrical alternating potential through an asymmetrical transmission channel, a non-linear resistance, means including said resistance for developing a continuous potential component in accordance with the asymmetry of said alternating potential, means for producing a continuous potential from said component and ior storing such potential, means responsive to said stored potential for supplying said asymmetrical alternating potential to saidchannel in such phase that the asymmetry of said alternating potential corresponds to the asymmetry of said channel, and means for preventing the operation of said last means during the presence oi said alternating potential.

3. In combination, in a system for transmitting an asymmetrical alternating potential through an asymmetrical transmission channel. a non-linear resistance, means for impressing said potential across said resistance to develop a continuous potential in accordance with the asymmetry of said alternating potential, a bridge having an arm including the dimharge path of an electron discharge device having a control electrode, said bridge being balanced'when no potential i impressed on said control electrode, a source of operating potential for said device connected across one diagonal of said bridge, means for DAVID DAVIS.

- supplying said asymmetrical potential to said channel in polarity dependent on the polarity of 

